GB2178487A - I.C. engine carburettor fuel cut-off mechanism - Google Patents
I.C. engine carburettor fuel cut-off mechanism Download PDFInfo
- Publication number
- GB2178487A GB2178487A GB08618409A GB8618409A GB2178487A GB 2178487 A GB2178487 A GB 2178487A GB 08618409 A GB08618409 A GB 08618409A GB 8618409 A GB8618409 A GB 8618409A GB 2178487 A GB2178487 A GB 2178487A
- Authority
- GB
- United Kingdom
- Prior art keywords
- inlet manifold
- vacuum
- pressure responsive
- responsive device
- diesel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M3/00—Idling devices for carburettors
- F02M3/02—Preventing flow of idling fuel
- F02M3/04—Preventing flow of idling fuel under conditions where engine is driven instead of driving, e.g. driven by vehicle running down hill
- F02M3/045—Control of valves situated in the idling nozzle system, or the passage system, by electrical means or by a combination of electrical means with fluidic or mechanical means
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)
Abstract
A rigid, gas impervious enclosure 6 connected via a vacuum line 7 to the inlet manifold has therein a pressure responsive bellows 8 which operates a switch 9 to cause closure of an anti-diesel valve controlling the idling fuel supply when the vacuum in the enclosure exceeds a predetermined threshold. The enclosure isolates the bellows from atmospheric pressure variations. <IMAGE>
Description
SPECIFICATION
Fuel control mechanism
The present invention is concerned with fuel control mechanisms for use in combination with internal combustion engines.
Fuel and air are conventionally mixed for supply to an internal combustion engine by means of a throttle controlled carburettor; when the throttle is closed, a small amount of fuel is supplied to the engine by means of idler fuel supply which operates in response to a partial vacuum being created in the engine's inlet manifold.
A drawback of such an arrangement is that when a vehicle powered by the engine is decelerated, a vacuum is created in the inlet manifold, which unnecessarily operates the idler fuel supply with consequent waste of fuel and resulting contamination of the exhaust.
Some carburettor designs incorporate a solenoid operated valve the function of which is to control the idler fuel supply; one such type of valve (called an anti-diesel valve) is operated by the ignition circuit, so that when the ignition is switched on, the valve is energised so as to open the idler fuel supply, and when the ignition is switched off the valve is deenergised so as to close the idler fuel supply.
It is further known to provide a solenoid-operated valve arranged to respond to an increase in the vacuum (that is a decrease in the pressure) in the inlet manifold during deceleration to cut off flow of fuel from the idler fuel supply during such deceleration periods; an example of such an arrangement is disclosed in U.K. Patent Specification No 1350423. In the arrangement disclosed in the latter specification, the increase in the vacuum (decrease in pressure) is detected by means of a pressure switch comprising a seaied housing supporting a flexible diaphragm connected via a vacuum line to the inlet manifold; reduction in the pressure in the inlet manifold (as during deceleration) causes inward deformation of the diaphragm, which thereby operates an electrical switch controlling the solenoid to cut off the idler fuel supply.I have found that a disadvantage of the arrangement described is that, because the diaphragm is open to the atmosphere, it responds to changes in ambient pressure, so that under high ambient pressure conditions the idler fuel supply is cut off earlier than would be desirable, while under low ambient pressure conditions, cut off is delayed.
I have therefore devised a fuel control mechanism in which this disadvantage is substantially alleviated.
According to the present invention, therefore, there is provided a fuel control mechanism for use in combination with an internal combustion engine having a carburettor, an inlet manifold, and an ignition circuit controlled anti-diesel valve arranged to prevent idler fuel supply from the carburettor to the inlet manifold when the ignition circuit is "off", in which the inlet manifold is in pneumatic communication with a pressure responsive device which is arranged to operate said anti-diesel valve when the vacuum in the inlet manifold exceeds a predetermined threshold, said pressure responsive device being isolated from ambient pressure variations.
The pressure responsive device may be disposed directly in the inlet manifold; however, it is particularly preferred to employ a pressure responsive device disposed in a rigid, gas-impervious enclosure connected via a vacuum line to the inlet manifold.
The term "rigid", as used herein, means substantially without response to changes in ambient atmosphere pressure. Clearly, in the case where a rigid enclosure is connected to the inlet manifold by a vacuum line, the latter is also rigid (and gas impervious) in order to ensure that the pressure responsive device is isolated from ambient pressure variations.
The fuel control mechanism according to the invention is such that the anti-diesel device cuts off fuel supply to the inlet manifold when the vacuum in the latter (or in the above-mentioned rigid enclosure) exceeds a predetermined threshold, for example, during deceleration, braking, or going downhill. This predetermined threshold corresponds to that obtained by idling the engine while stationary; the predetermined threshold is reached in any condition where the engine has a greater number of revolutions per minute than in the idling stationary condition with the throttle closed.
A specific embodiment of the present invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a conventional inlet manifold with idler fuel supply and anti-diesel device;
Figure 2 is a graph of vacuum versus RPM for an exemplary internal combustion engine, with throttle closed;
Figure 3 is a schematic representation of an exemplary pressure responsive device for use in a fuel control mechanism according to the invention; and
Figure 4 is a schematic representation of
(a) conventional electrical supply to an antidiesel device; and
(b) electrical supply to anti-diesel device in a fuel control mechanism according to the invention.
Referring to Fig. 1, an inlet manifold 1 having a throttle 2 is supplied with fuel from an idler fuel supply 3 from a carburettor (not shown). The flow of fuel along the idler fuel supply 3 is controlled by an adjusting screw 4, and can be stopped completely by antidiesel solenoid 5 (shown in the energised condition).
Referring now to Fig. 2, the abscissa is cali brated in r.p.m, while the ordinate is calibrated in the degree of vacuum with throttle closed.
At level C is a typical degree of vacuum (23 inches of mercury) obtained while idling stationary (750 r.p.m.). The pressure responsive device in the fuel control mechanism according to the invention is such that it operates the anti-diesel valve when level C is exceeded by more than a predetermined amount (for example, when the vacuum degree is from B to A).
Referring to Fig. 3, there is shown a rigid gas impervious enclosure 6 connected to the inlet manifold (not shown) by a vacuum line 7.
Within the enclosure is an aneroid bellows 8, in contact with one face of which is an electrical switch 9 which is mechanically actuated by bellows 8. The switch 9 is connected by leads 10 to the solenoid (not shown) which controls the engines anti-diesel valve. The pressure in the enclosure 6 at which the switch 9 is caused to actuate is pre-set by adjustment screw 11. It is particularly preferred that the combined volume of enclosure 6 and vacuum line 7 should be only a small proportion of the total displacement of the engine (for example, less than about 4% thereof).
Referring to Fig. 4(a), this shows the conventional eletrical supply to the solenoid of an anti-diesel valve. When the ignition is switched on by switch 12, the circuit is complete and the solenoid 13 is energised.
When a pressure responsive switch 9 (for example, as described above with reference to
Fig. 3) is employed, as in Fig. 4(b), it can be see that the switch can control operation of the solenoid 13 when the ignition is on.
Claims (4)
1. A fuel control mechanism for use in combination with an internal combustion engine having a carburettor, an inlet manifold, and an ignition circuit controlled anti-diesel valve arranged to prevent idler fuel supply from the carburettor to the inlet manifold when the ignition circuit is "off", in which the inlet manifold is in pneumatic communication with a pressure responsive device which is arranged to operate said anti-diesel valve when the vacuum in the inlet manifold exceeds a predetermined threshold, said pressure responsive device being isolated from ambient pressure variations.
2. A mechanism according to claim 1, in which the pressure responsive device is disposed in a rigid, gas impervious enclosure connected via a vacuum line to the inlet manifold.
3. A mechanism according to claim 1 or 2, in which the pressure responsive device comprises aneroid bellows arranged to mechani caliy actuate an electrical switch controlling said anti-diesel device when the vacuum detected by said bellows exceeds said threshold.
4. A fuel control mechanism substantially as described herein with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8519455 | 1985-07-30 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8618409D0 GB8618409D0 (en) | 1986-09-03 |
| GB2178487A true GB2178487A (en) | 1987-02-11 |
Family
ID=10583218
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08618409A Withdrawn GB2178487A (en) | 1985-07-30 | 1986-07-29 | I.C. engine carburettor fuel cut-off mechanism |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2178487A (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0079763A1 (en) * | 1981-11-16 | 1983-05-25 | John Eastman Barnes | Idle mixture adjusting device with fuel cut-off during deceleration |
-
1986
- 1986-07-29 GB GB08618409A patent/GB2178487A/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0079763A1 (en) * | 1981-11-16 | 1983-05-25 | John Eastman Barnes | Idle mixture adjusting device with fuel cut-off during deceleration |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8618409D0 (en) | 1986-09-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |